One is familiar with many methods for the manufacture of packaging bags that include opening and closing zippers equipped with sliders.
FIG. 1 shows that some of these methods include a step that consists of forming bags 2 in a scrolling film 1, and a step that consists of welding, onto the bags 2 thus formed, opening and closing zippers 3 that include a series of operating sliders 4.
The opening and closing zippers 3 generally include additional zipper devices, and each slider 4 allow the opening or closing of a bag 2 by locking the zippers together, or not, as the slider is moved along the zippers.
On some packaging machines, it is preferable that the zippers 3 should be welded continuously.
Given the variations of pitch length 5 of the sliders 4 on the zippers 3 and the variations of pitch length 6 of the bags during manufacture, it is necessary of readjust each slider 4 to the desired pitch 6 of the bag 2.
To this end, the solution is to weld, onto the bags 2, zippers 3 that are equipped with sliders 4 whose pitch 5 is slightly less than the pitch 6 of the bags 2, so that with the tolerances in the pitch 5 and 6, the maximum length 40 of a zipper fitted with a slider 4 is always less than the minimum pitch dimensions 6 of a bag 2.
However, as shown in FIG. 2, by readjusting the slider 4 to the pitch 6 of the bag 2, then after the manufacture of n bags, one finds oneself with two sliders 4 on one bag 2 in rank n. In fact one has a bag width 6′ that differs from the desired pitch 6 of the bags.
Currently, the bag 2 in rank n is marked as defective and ejected from the production line.
This creates a rupture in the production chain which in fact it is desired should be continuous.
This also causes the loss of the whole bag, and therefore a manufacturing overcost if this happens very often.